Refactor extension to webpack

This change is the biggest in the history of the project. The entire
project has been refactored so it is built with webpack.

This involves:
- Creating webpack and npm config files.
- Fixing some bugs in the code due to the fact that webpack uses strict
mode.
- Merging some pieces of code which were shared throughout the codebase
(not exhaustive, more work should be done in this direction).
- Splitting the console_inject.js file into separate files (it had 1000+
lines).
- Adapting all the build-related files (Makefile, bash scripts, etc.)
- Changing the docs to explain the new build process.
- Changing the Zuul playbook/roles to adapt to the new build process.

Change-Id: I16476d47825461c3a318b3f1a1eddb06b2df2e89
diff --git a/src/common/extUtils.js b/src/common/extUtils.js
new file mode 100644
index 0000000..a1b4d48
--- /dev/null
+++ b/src/common/extUtils.js
@@ -0,0 +1,13 @@
+// This method is based on the fact that when building the extension for Firefox
+// the browser_specific_settings.gecko entry is included.
+export function isFirefox() {
+  var manifest = chrome.runtime.getManifest();
+  return manifest.browser_specific_settings !== undefined &&
+      manifest.browser_specific_settings.gecko !== undefined;
+}
+
+// Returns whether the extension is a release version.
+export function isReleaseVersion() {
+  var manifest = chrome.runtime.getManifest();
+  return ('version' in manifest) && manifest.version != '0';
+}